Implantable blood pumps are typically used in the later stages of heart disease or after trauma to the heart, when the heart itself is too weak or otherwise incapable of creating sufficient blood pressure and blood circulation to satisfy body function.
Various blood pumps are already in use for the purpose of augmenting or replacing the blood pumping action of damaged or diseased hearts. Blood pumps are commonly used in three situations: (1) for acute support during cardio-pulmonary operations; (2) for short-term support while awaiting recovery of the heart from surgery; or (3) as a bridge to keep a patient alive while awaiting heart transplantation. The pumps may be designed to provide at least one of right or left ventricular assist, although left ventricular assist is the most common application in that it is far more common for the left ventricle to become diseased or damaged than it is for the right ventricle.
Implantable blood pumps comprise miniaturized pumps capable of being percutaneously or surgically introduced into or adjacent to the vascular system of a patient, typically to provide left or right heart support, or even total heart support. Various types of blood pumps include radial flow centrifugal pumps and axial flow pumps. Such pumps typically use magnetic or electromagnetic forces, for example, to power a magnetic rotor placed within or adjacent to a flow path of blood moving into or out of the heart. An at least one electromagnet, or stator, is positioned around the outside of a tubular casing containing the flow path, whereas the rotor is disposed inside the casing.
The rotor is magnetic. The stator typically is a set of electrically conductive wire coils. The rotor is energized by a power source with alternating currents through the coils to create a rotating magnetic field. That is, the field is directed transverse to the axis of the tubular casing, and the direction of the field rotates about the axis of the casing. As the field rotates, the rotor spins about its axis thus advancing the blood within the flow path. The power source may be implanted somewhere within the body of the patient or may be external to the patient, as is known in the art.
One such pump, disclosed in U.S. Pat. No. 7,575,423, the entirety of which is incorporated by reference herein as if fully set forth herein, is a centrifugal-type pump. FIGS. 3 and 7 of U.S. Pat. No. 7,575,423 have been reproduced herein as FIGS. 1 and 2, and illustrate a centrifugal-type implantable blood pump including a housing 14, defining the flow path for blood passing through the device. This device also includes a stator 56 having a metal wire coil or winding 57. A common metal used in such stators is copper wire. Around the stator is a second housing 12 which forms a seal around the stator and, once the pump is implanted into a patient in need thereof, prevents surrounding body fluids from contacting the stator.
While current implantable blood pumps provide numerous benefits to patients in need thereof, improvement can be made to the current devices to provide additional benefits to patients, in addition to potentially making such devices available to an even wider range of patients in need thereof.